GitLab

sheaf pushed to branch wip/T23210 at Glasgow Haskell Compiler / GHC

Commits:

78bb735d

by Ben Gamari at 2025-09-16T12:56:15+02:00

StgToByteCode: Don't assume that data con workers are nullary

Previously StgToByteCode assumed that all data-con workers were of a
nullary representation. This is not a valid assumption, as seen
in #23210, where an unsaturated application of a unary data
constructor's worker resulted in invalid bytecode. Sadly, I have not yet
been able to reduce a minimal testcase for this.

Fixes #23210.

521b9264
by Ben Gamari at 2025-09-16T12:56:15+02:00
```
testsuite: Mark T23146* as unbroken
```

3 changed files:

compiler/GHC/StgToByteCode.hs
rts/Interpreter.c
testsuite/tests/codeGen/should_run/T23146/all.T

Changes:

compiler/GHC/StgToByteCode.hs

@@ -2331,11 +2331,12 @@ pushAtom d p (StgVarArg var)
          -- PUSH_G doesn't tag constructors. So we use PACK here
          -- if we are dealing with nullary constructor.
          case isDataConWorkId_maybe var of
 -          Just con -> do
 -            massert (isNullaryRepDataCon con)
 -            return (unitOL (PACK con 0), szb)
 +          Just con
 +            -- See Note [LFInfo of DataCon workers and wrappers] in GHC.Types.Id.Make.
 +            | isNullaryRepDataCon con ->
 +              return (unitOL (PACK con 0), szb)
 -          Nothing
 +          _ ->
              -- see Note [Generating code for top-level string literal bindings]
              | idType var `eqType` addrPrimTy ->
                return (unitOL (PUSH_ADDR (getName var)), szb)

rts/Interpreter.c

@@ -2227,7 +2227,6 @@ run_BCO:
              // n_nptrs=1, n_ptrs=0.
              ASSERT(n_ptrs + n_nptrs == n_words || (n_nptrs == 1 && n_ptrs == 0));
              ASSERT(n_ptrs + n_nptrs > 0);
 -            //ASSERT(n_words > 0); // We shouldn't ever need to allocate nullary constructors
              for (W_ i = 0; i < n_words; i++) {
                  con->payload[i] = (StgClosure*)ReadSpW(i);
+             }

testsuite/tests/codeGen/should_run/T23146/all.T

  test('T23146', normal, compile_and_run, [''])
  test('T23146_lifted', normal, compile_and_run, [''])
 -test('T23146_liftedeq', expect_broken_for(23060, ghci_ways), compile_and_run, [''])
 +test('T23146_liftedeq', normal, compile_and_run, [''])
  test('T23146_lifted_unlifted', normal, compile_and_run, [''])